Electrical device



April 15, 1958 N. c. JAMISON 2,831,149

ELECTRICAL DEVICE Filed-July 13. 1950 2 arcmo/vsmaw HECTMWEM MODULATING vounse 7 4. 171 a Z1 .a f 18 K 7 LUJJ/ Eur-par Eour nur 16 mpur INPUT c fi'll l MODULAT/NG VULTA GE 8 E C ONO MODULITING vol. TA 66 wpur MODULAT/NG VOL me:

NOEL GQMMZSON INVENTOR.

United States Patent ELECTRICAL DEVlCE Noel C. Jamison, Irvington-on-Hudson, N. Y., assignor, by mesne assignments, to North American Philips Company, Inc., New York, N. Y., a corporation of Delaware Application July 13, 1950, Serial No. 173,494 7 Claims. (Cl. 315- 55) now Patent 2,749,471 issued June 5, 1956 there is disclosed a novel electron discharge tube employing a photoconductive semi-conductor, such as germanium, silicon, thallous sulfide, lead sulfide and selenium, as the principal element of the anode structure. The semi-conductor materials disclosed therein all have the common attribute that the internal conductivity thereof is altered both by light and by electrons impinging thereon.

l have now found that the amplification characteristics of such tubes can be substantially improved in certain respects by employing a more complex anode which is responsive to electron impact for the photo-conductive semi-conductor and that by employing this novel anode element, large amplification factors with improved linearity can be readily realized at the usual current densities encountered in the operation of a conventional electron discharge tube.

Briefly, the device according to the invention employs an anode constituted by a barrier layer cell. A barrier layer cell as referred to herein comprises a semiconductor separated from a conductive or counter-electrode by a barrier layer and a terminal electrode in intimate electrical contact with the semi-conductor. Two well-known examples of these cells are the selenium barrier layer cell employing a semi-conductive selenium layer separated from a thin counter-electrode by abarrier layer formed from the selenium or independently applied thereover; and the copper oxide cell employing a copper metal plate which has been oxidized to form a layer of cuprous oxide, the barrier layer being formed at' the interface of the copper and cuprous oxide.

.These barrier layer cells may be further arranged for electron bombardment in one of two ways; that is, the cell may be arranged so that the electrons can penetrate the counter-electrode and impinge upon a barrier layer, while in the other type, the electrons can penetrate the terminal electrode, enter a semi-conductor and impinge upon a barrier layer.

I have found that when these cells are subjected to electron bombardment, electrons apparently penetrate the outer electrode or electrodes and impinge upon the barrier, which results in the generation of an E. M. F. and flow of current in an output circuit which is dependent upon the intensity of the electron beam and the velocity of impact of the electrons on the cell. Other energy sources in the output circuit are not required,

This makes possible the use of tubes embodying a complex anode construction of the above-described type in amplifiers, modulators and in other applications of electron discharge devices. When employed properly in a suitable circuit, the tube has a reasonably flat response 2,831,149 Patented Apr. 15, 1958 2: over the range of audio frequencies. Because of the very low internal impedance of these cells when operat ing as-self-g'enerators of an E. M. F., it has been found preferable to employ a low impedance output circuit.

The current output of the cell. is substantially linear in response to electron bombardment for a low impedance in the external circuit. This characteristic of the tube readily adapts it for use in amplifier circuits where substantial linearity of output is desired.

The tube may also be arranged to operate over a nonlinear portion of its plate current-plate voltage characteristic with a suitabl'echoice of operating potentials applied to the anode and control electrodes, thus adapt"- ing the tube for use in a circuit in which one signal is to be modulated by a second signal. In this arrangement the signal to be modulated can be applied to the control grid and the modulating potential applied between the anode and the cathode and the resulting modulated signal derived across a low impedance output, in which case amplification of the modulated signal also occurs across the cell. v d

It is also possible to modulate a carrier signal by introducing the modulating potential directly across the cell. In this arrangement, in order to operate on a nonlinear portion of the cell current-voltage characteristic, it may be'foun'd desirable to apply a bias potential across the cell, i. e. a voltage of such magnitude as to be greater than where k is Boltzmanns constant, T the absolute temperature, and E the electronic charge, which voltage equals approximately 25 millivolts at ambient temperature and less than that which neutralizes the space charge of the barrier layer, when applied in the forward di-' rection.

While the invention will be described with particular reference to triode structures, it should be noted that a simple diode arrangement employing the barrier layer cell as the anode may also serve to demodula'te a coin plex voltage applied between the cathode and the anode,

the components of which canbe' derived either across a load resistance between the anode and cathode or directly across the cell, making use of the non-linear voltage current characteristic of either the cell or of the tube. In this connection, it is also possible to introduce an alternating current voltage between the anode and cathode, in which case the tube will rectify the alternating. cur rent voltage and the cell-will amplify the rectified cur rent thus produced.

The invention will be described furtherwith reference to the appended drawing, in which:

Fig. 1' shows a tube employing a complex anode-com stru'ction according to the invention in a simple a'mpli-" fier circuit;

Fig.2 shows on an enlarged scale, one forniof anode construction; V

Fig.3 shows on an enlarged scale, another form ofthe' anode construction;

Fig. 4' shows a tube according to the invention, er'nployed in a circuit with a bias potential applied across the cell;

Fig. 5 shows a tube according to the invention end ployed in one form of modulator circuit;

Fig. 6 shows a tube according to the invention in which modulation occurs in the cell;

Fig. 7 shows a tube according to the invention in which the tube-modulates two voltages; and

Fig. 8 shows a partial cutaway view of a tube structure according to the invention,

Referring to the drawing, {the tube 1' in Fig. 1 emitprises a cathode 2, a control electrode 3, and a complex anode 4 constituted by a barrier layer cell of the type described above. An input voltage is applied between the control electrode and the cathode, while an output voltage is derived from the cell through transformer 5. An accelerating potential is supplied to the anode by battery 6. As will be noted, there are two lead connections to'the cell 4, which connections together with the transformer 5 represent the output circuit for the tube.

The impinging electrons on the cell 4 are thus distinct from the output connections to the cell 4. Note also thatthe output circuit is itself free of other energy sources.

The anode construction can be more clearly seen from Figs. 2 and 3, in which the arrangement of the electrode elements with respect to the cathode can be more clearly seen since the electrodes and the barrier layer have been greatly exaggerated in size for the sake of clearness. In Fig. 2, the electrons penetrate a very thin, continuous counter-electrode 7 and impinge upon the barrier layer 8 (which is greatly exaggerated; normally the barrier layer is of the order of 10'' to 10- cm. thick). Beyond the barrier layer isthe semi-conductor body 9, e. g. selenium or cuprous oxide, and on that side of the semiconductor remote from the cathode is the terminal electrode 10, which, together with the counter-electrode 7, provide electrical connections to the semiconductor. This form of cell construction is sometimes referred to as a front wall cell which is to be distinguished from and preferred to a back-wall cell, which will be described in connection with Fig. 3. To employ modern terminology, the electrode 10 would be considered an ohmic base connection to the semi-conductor body 9, and the electrode 7 would be considered a rectifying connection to the semi-conductor 9, since between it and the semi-conductor 9 exists a barrier layer or rectifying junction. It will also be understood that the barrier layer need not be a separate, different material from that of the semi-conductor 9, but could also be the contact interface between the counter-electrode 7 and the body 9, enabling arectifying effect to be obtained.

Fig. 3 shows a back-wall cell. In this cell, electrons penetrate a very thin metal terminalelectrode 11 which makes electrical contact with a semi-conductor electrode 12. The electrons continue to penetrate the semi-conductor which, in this case, must also be very thin, and impinge upon the barrier layer 13 or rectifying junction, on the other side of which is the counter-electrode 14.

Figs. 4 to 7 show various simple circuit arrangements for employing the tube as an amplifier, a modulator, and a multiplex modulator. In Fig. 4, the tube is shown as an amplifier with a bias potential applied across the cell by battery 15. With a bias voltage across the cell, the current-voltage characteristic becomes non-linear, thus adapting the tube for use as a modulator. By control of the bias, different results may be obtained, such as a constant ratio of induced current in the semi-conductor to electron beam current.

In Fig. 5 a first signal voltage is applied between thecontrol electrode and the cathode, and a second modulating voltage is applied between the anode and cathode through the transformer 16, the modulated signal being derived across the cell through transformer 17.

23. The electrodes are mounted on a support 24 and comprise a cylindrical cathode 25 which may be either of the directly or indirectly heated type, a mesh or grid electrode 26 and a complex anode 27 of the above-do scribed type having a multilayer construction, as will be seen from the drawing.

In describing the invention, it has been reduced to its essentials but it should be obvious that while only one control or grid electrode has been shown, additional electrodes could be provided. In this respect, it is within the contemplation of the invention to employ a screen electrode, a suppressor electrode, beam forming electrodes or a multi-electrode construction in which the anode has a cell construction of the above type. It is also within the purview of the invention to employ this tube in circuits of a more complex nature in which various signal elfectsare achieved without departing from the basic purpose of the invention.

While I have thus described the invention with specific embodiments and applications thereof, it will be obvious to those skilled in the art that the invention is capable of various modifications and applications without departing from the spirit and scope of the invention as defined in the appended claims.

. WhatI claim is:

1. An electron discharge device comprising an evacuated envelope, a cathode, a control electrode, and an anode comprising a selenium barrier layer cell arranged for electron bombardment from said cathode.

2. An electron discharge device comprising an evacuated envelope, a cathode, a control electrode, and an anode comprising a counter-electrode, a semi-conductive selenium layer defining a barrier layer with said counterelectrode, and a conductive terminal electrode in contact with the selenium layer and arranged in that order with respect to the cathode.

3. An electrical device comprising a body of semiconductive material constituted of selenium and including an ohmic base connection and a rectifying connection to said body at a region thereof spaced from said base connection, means for producing electrons impinging against the surface of said body in proximity to said rectifying connection, and an output circuit distinct from said impinging electrons and coupled to said ohmic and rectifying connections.

4. Anelectrical device comprising a body of SGHlirCOIlductive material,-means for producing electrons impinging against a surface portion of said body, a thin, continuous,-,,electron-permeable electrode abutting and extending oversaid entire surface portion of said body on which electrons impinge, another electrode connected to said body, said body including a barrier layer between the two electrodes, said electron-permeable electrode being of such thinness that impinging electrons penetrate said electrode and impinge upon the body in the vicinity of said barrier layer, and an output circuit, distinct from In Fig. 6 the modulating voltage is introduced directly acrossthe cell through transformer 18'and the modulated signal derived through transformer 18a. In Fig. 7 two modulating voltages may be introduced for modulating the signal applied to the control electrode. One modulating voltage is applied between the anode and cathode through transformer 19, the second modulating voltage is applied across the cell through transformer 20, the modulated signal being derived across the cell through transformer 21.

In Fig. 8 I have shown a typical tube structure embodying the invention. The tube is of conventional construction employing an envelope 22 attached to a base said impinging electrons, coupled to said two electrodes and thus across said barrier layer.

5. A device as set forth in claim 4, wherein the electron-permeable electrode comprises a thin, metal film overlying said entire surface portion.

6. An electrical device generating an electromotive force comprising a semi-conductive body, an ohmic base connection to said body, a rectifying connection to said body and spaced from said base connection and defining a rectifying junction thereat, means for producing electrons impinging upon the body in proximity to said rectifying junction thereby to generate an electromotive force available at the pair of connections, and an output'circuit free of other energy sources and distinct from said impinging electrons for abstracting and utilizing said genthe entire surface of the body on which the electrons impinge, said impinging electrons penetrating the electronpermeable electrode to interact with the rectifying junction.

References Cited in the file of this patent UNITED STATES PATENTS Gentry May 16, 1933 Iams Oct. 10, 1939 Benzer n Dec. 16, 1952 

1. AN ELECTRON DISCHARGE DEVICE COMPRISING AN EVACUATED ENVELOPE, A CATHODE, A CONTROL ELECTRODE, AND AN ANODE COMPRISING A SELENIUM BARRIER LAYER CELL ARRANGED FOR ELECTRON BOMBARDMENT FROM SAID CATHODE. 